Low temperature, moisture-curable coating compositions are desirable in many applications. For example, such coating compositions are, in at least some cases, preferable over, for example, thermally-cured or radiation cured coating compositions because (i) little or no energy is required to cure the composition, (ii) the materials from which some substrates are constructed cannot withstand elevated temperature cure conditions, and/or (iii) large or complex articles to be coated may not be convenient for processing through thermal or radiation cure equipment.
Some coating compositions are based on the hydrolysis and condensation of silane based materials that form a crosslinked Si—O—Si matrix. These compositions often form hard, highly crosslinked films, which are limited in flexibility. Therefore, the resultant coatings are often susceptible to chipping or thermal cracking due to embrittlement of the coating film. Moreover, such films can be especially unsuitable for use in coating substrates that can bend or flex, such as elastomeric automotive parts and accessories, for example, elastomeric bumpers and body side moldings, as well as consumer electronics equipment, among other things. The coating compositions applied to such elastomeric substrates typically must be very flexible so the coating can bend or flex with the substrate without cracking.
As a result, it would be desirable to provide low temperature, moisture curable coating compositions that are capable of producing a flexible, crack resistant coating when applied to a substrate and cured. Moreover, it would be desirable to provide such coating compositions that are, in at least some cases, substantially solvent free, sprayable at room temperature, and/or storage stable. In addition, it would be desirable to provide means for improving certain properties of such coating compositions, such as the initial (within 6 hours after application) scratch resistance of coatings deposited from such compositions without significantly detrimentally impacting other coating properties, such as appearance, flexibility and adhesion.